Advances in computing and networking technology have led to the development of new and increasingly complex communications networks, Today, for example, systems such as the Universal Mobile Telecommunications System (UMTS) seek to provide mobile phones, personal computers, and other computing devices with wireless access to the Internet and other networks.
FIG. 1 is a schematic diagram of a UMTS network. As shown in FIG. 1, a mobile radio network generally includes a set of base stations and base station controllers. In the UMTS, this network is called the UMTS Terrestrial Radio Access Network (UTRAN), a base station is called a Node B, and a base station controller is called a Radio Network Controller (RNC).
The UTRAN communicates both with mobile terminals, known as User Equipments (UE), via a Uu interface, and with a Core Network (CN) via an Iu interface. As shown in FIG. 1, the RNCs are connected:                to the Node B via an Iub interface;        to each other via an Iur interface; and        to the Core Network CN via an Iu interface.        
The core network CN typically includes equipment for performing circuit and packet switching. For example, the core network CN may include one or more mobile switching centres (MSCs) (not shown) for enabling communication over the public switched telephone network (PSTN). The core network CN may also include a gateway general packet radio service (GPRS) support node (GGSN) (not shown) for interfacing to external packet-based networks such as the Internet. The interface between the RNCs and the MSC is known as Iu-cs, and the interface between the RNCs and the GGSN is Iu-ps.
The resource allocation within the system is important to maintain the flow of traffic. It is typical for two parties (such as an operator and the seller of the RNC) to describe, in a “Service Level Agreement” (SLA), the conditions for flow rates across interfaces. For example, the SLA may indicate that the operator has bought 50 Mbps Iub-max capacity (i.e. he has agreed that the maximum throughput across the Iub should not exceed 50 Mbps). The seller of the RNC may well provide more Iub capacity than the required 50 Mbps, but the traffic must be limited below the agreed capacity. The SLA is thus not usually enforced by the limitations of the hardware. The preferred solution is to provide more powerful hardware and enforce the SLA using software.
In many cases there is no direct mapping between the SLA and the required hardware. For example, aggregate Iub throughput (Iub-max) may be sold, but each RNC is connected to several RBSs through the Iub transport network. When the Iub Transport Network is dimensioned for this throughput, then the total peak capacity of Iub must be larger than the licensed capacity, because of spatial variation of the traffic. At the same time, the sum throughput of the interfaces must also be limited to ensure that the license level is not exceeded. In addition, the Iub transport network is owned by the operator and can easily be upgraded. A specific software solution for this purpose is desirable to enforce the limit.
There are two ways of limiting the throughput of an interface: shaping and policing. In the case of shaping, buffering is used, and the serving rate of the buffer is set to the required maximal throughput. In the case of policing, the out-of-profile packets are dropped without any buffering.
Where shaping is used, the packet delay is increased by buffering when the traffic is saturated. Self-clocking protocols such as the Transmission Control Protocol (TCP) can react on this delay increase by rate reduction, and in this way resolve the congested situation. This buffering method is used in IP routers and is TCP friendly by nature.
In some situations buffering is not allowed, or extra buffering delays to the in-profile packets are not desirable. In these situations shaping cannot be used and the throughput must be limited by policing. Several policing methods exist: one example is the Committed Access Rate (CAR) method of Cisco.
It is desirable to license RNC capacity so that it can operate with more than one interface. This requires that the sum throughput of more than one interface should be limited. For example, if an operator has a license for 50 Mbps Iub capacity, but three 100 Mbps cards installed, the aggregate traffic should still be regulated below 50 Mbps. This requires a distributed RNC capacity licensing algorithm. The actual traffic on the involved interfaces must be measured. Action may then be taken, based on these measurements, to force the licensed capacity.